WordNet (r) 3.0 (2006):

slummy
    adj 1: (of housing or residential areas) indicative of poverty;
           "a slummy part of town"; "slum conditions"

Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "slummy":
   battered, beat-up, beaten up, broken-down, decrepit, derelict,
   dilapidated, in ruins, ramshackle, ruined, ruinous, run-down,
   shabby, slumlike, sordid, squalid, tottery, tumbledown, wretched